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The Linkage Between Garnets Found in India at the Arikamedu Archaeological Site and Their Source at the Garibpet Deposit

Authors:
  • PANGEMTECH Panjikar Gem Research & Tech Institute, Pune,India

Abstract and Figures

The archaeological site of Arikamedu, located in Tamil Nadu State on the east coast of India, was the centre for many centuries of a significant bead-producing industry. Beads were made of both glass and stone, including garnet, but the source of the garnet rough material has not been confirmed. To probe this question, garnet beads found at Arikamedu were compared with rough material from the Garibpet deposit, located approximately 640 km away in Telangana State, east of the city of Hyderabad, India. Samples from the two localities exhibited substantial correlation with respect to average composition, trace-element contents, chemical zoning of major and minor elements, inclusion assemblages and zoning of inclusions between the rims and cores of the crystals. Chemically, the stones were almandine rich (averaging 81.0% almandine, 11.5% pyrope, 3.3% spessartine and 1.5% grossular), with pronounced zoning for Mn and Mg. Zoning of trace elements also was observed, especially for Y, P and Zn. The most characteristic aspects of the inclusion pattern were sillimanite fibres that were concentrated in a zone between an inclusion-rich core and an inclusion-poor rim. In combination, the microscopic observations, identification of the inclusion assemblage, and chemical analyses established that the rough material used historically in the Arikamedu area to produce garnet beads originated from the Garibpet deposit. Furthermore, the results suggest that existing schemes for classifying historical garnets require additional refinement.
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Gemmology
Volume 35 / No. 7 / 2017
The Gemmological Association of Great Britain
The Journal of
Contents
iISSN: 1355-4565, http://dx/doi.org/10.15506/JoG.2017.35.7
This cloisonné-style disc brooch
(5.75 cm in diameter, from Un-
terhaching, near Munich, Ger-
many) is set with thin, doubly
polished garnet plates of up to
2.8 cm long and 1 mm thick.
The origin of such garnets in
early medieval European jew-
ellery is widely debated and
often attributed to India. A
provenance study focusing on
Indian garnet beads appears on
pages 598–627 of this issue. Photo by M. Eberle,
© Archäologische Staatssammlung, Munich, Germany.
ARTICLES
Feature Articles
598 The Linkage Between Garnets Found in India at the
Arikamedu Archaeological Site and Their Source at
the Garibpet Deposit
By Karl Schmetzer, H. Albert Gilg, Ulrich Schüssler, Jayshree
Panjikar, Thomas Calligaro and Patrick Périn
628 Simultaneous X-Radiography, Phase-Contrast
and Darkeld Imaging to Separate Natural from
Cultured Pearls
By Michael S. Krzemnicki, Carina S. Hanser and Vincent Revol
640 Camels, Courts and Financing the French Blue
Diamond: Tavernier’s Sixth Voyage
By Jack Ogden
652 Counterfeiting Gems in the 16th Century: Giovan
Battista Della Porta on Glass ‘Gem’ Making
By Annibale Mottana
668 Conferences
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Congress/European Gemmological Symposium
674 Gem-A Notices
676 Learning Opportunities
679 New Media
684 Literature of Interest
Gemmology
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Volume 35 / No. 7 / 2017
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572 Gem Notes
Cat’s-eye aquamarine from Meru,
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dravite from Tanzania|Enstatite
from Emali, Kenya|Grossular
from Tanga, Tanzania|Natrolite
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Cover Photo:
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p. 581
p. 586
598 The Journal of Gemmology, 35(7), 2017
Feature Article
The Journal of Gemmology, 35(7), 2017, pp. 598–627, http://dx.doi.org/10.15506/JoG.2017.35.7.598
© 2017 The Gemmological Association of Great Britain
The archaeological site of Arikamedu, located in Tamil Nadu State on the east
coast of India, was the centre for many centuries of a signicant bead-producing
industry. Beads were made of both glass and stone, including garnet, but the
source of the garnet rough material has not been conrmed. To probe this ques-
tion, garnet beads found at Arikamedu were compared with rough material from
the Garibpet deposit, located approximately 640 km away in Telangana State,
east of the city of Hyderabad, India. Samples from the two localities exhibited
substantial correlation with respect to average composition, trace-element con-
tents, chemical zoning of major and minor elements, inclusion assemblages
and zoning of inclusions between the rims and cores of the crystals. Chemically,
the stones were almandine rich (averaging 81.0% almandine, 11.5% pyrope,
3.3% spessartine and 1.5% grossular), with pronounced zoning for Mn and Mg.
Zoning of trace elements also was observed, especially for Y, P and Zn. The most
characteristic aspects of the inclusion pattern were sillimanite bres that were
concentrated in a zone between an inclusion-rich core and an inclusion-poor
rim. In combination, the microscopic observations, identication of the inclusion
assemblage, and chemical analyses established that the rough material used
historically in the Arikamedu area to produce garnet beads originated from the
Garibpet deposit. Furthermore, the results suggest that existing schemes for
classifying historical garnets require additional renement.
The Linkage Between Garnets Found in
India at the Arikamedu Archaeological Site
and Their Source at the Garibpet Deposit
Karl Schmetzer, H. Albert Gilg, Ulrich Schüssler, Jayshree Panjikar,
Thomas Calligaro and Patrick Périn
Introduction
During the Hellenistic and Roman eras, garnets
in the red-to-purple colour varieties were one of
the most appreciated and expensive gem min-
erals. Principal uses spanned from functional to
aesthetic: They were both engraved as seals and
set in jewellery pieces. In the ancient world, the
extensive use of garnet—anthrax in Greek; car-
bunculus in Latin—can be traced from approxi-
mately 300 bc to the end of the western Roman
Empire (5th century ad). Usage continued in the
Early Middle Ages (5th–7th century ad or even
Garnets from Arikamedu and Garibpet, India
Feature Article
599
somewhat later, e.g. in Scandinavia), with garnet
becoming the dominant gem mineral in jewel-
lery. The setting of at, doubly polished garnet
plates into a metal framework (see photo on the
cover of this issue) is one form of the so-called
cloisonné work used in the past (cloisonné is
French for ‘partitioned’). In central Europe, the
extensive use of garnets in personal jewellery
then decreased throughout the course of the 6th
century ad and disappeared almost entirely in the
7th century, a period associated with a suspected
closure of sea routes to India by the Sasanians and
later by the Muslim Arab invasion (Rupp, 1937;
Whitehouse and Williamson, 1973; Roth, 1980;
Sidebotham, 1991; von Freeden et al., 2000; Len-
nartz, 2001). The causative relationship, however,
has been questioned, and other factors—includ-
ing changes in fashion and/or burial habits con-
comitant with Christianization—may have con-
tributed to the decline in garnet use (Calligaro et
al., 2006–2007; Gilg et al., 2010; Drauschke, 2011;
Sorg, 2011). Summarizing the various periods in
which garnet played an important role in glyptic
and jewellery, Adams (2011) referred to the span
from 300 bc to ad 700 as the ‘garnet millennium’.
The origin of the primary garnet material used
in the ancient world and the Early Middle Ages,
and correlation with information found in texts
penned by the authors of classical antiquity (pri-
marily Theophrastus and Pliny the Elder), was a
matter of largely unsupported speculation for dec-
ades. The initial examinations used physical and
structural properties (e.g. SG, RI or unit cell di-
mensions obtained by X-ray diffraction analysis),
but interpretations were highly ambiguous in the
absence of chemical data. A major step forward
was achieved when scientists began to apply non-
destructive analytical techniques that measured
the complete chemical composition of garnet sam-
ples found in early medieval jewellery or excavat-
ed at historical sites. Moreover, such results could
then be compared with data obtained for garnets
from modern sources (e.g. Löfgren, 1973; Rösch
et al., 1997; Farges, 1998; Greiff, 1998; Quast and
Schüssler, 2000; Calligaro et al., 2002).
Classication Schemes for
Historical Garnets
Building on the advancements mentioned above,
Calligaro et al. (2002) subdivided early medi-
eval garnets into ve different types primarily
by means of major- and trace-element composi-
tion, with a smaller contribution coming from the
identication of inclusions in a limited number of
samples. As shown in Table I, these subdivisions
comprised two types of almandine with different
Mn, Ca, Cr and Y contents (Types I and II), two
types of pyrope with different Cr levels (Types IV
and V) and one intermediate pyrope-almandine
type with variable composition (Type III). Fur-
ther studies rened the ve types (Calligaro et al.,
2006–2007; Périn and Calligaro, 2007; Calligaro et
al., 2009; Gast et al., 2013; Bugoi et al., 2016), and
the scheme was applied, in general, to additional
groups of early and even late medieval garnets by
other researchers (e.g. Mathis et al., 2008; Greiff,
2010; Horváth and Bendö, 2011; Šmit et al., 2014).
Nonetheless, despite the foregoing progress,
problems remain in any attempt to assign histori-
cal garnets to various types or groups. As noted,
Calligaro et al. (2002) performed the main sub-
division of garnets into different types by means
of spot chemical analysis, and for a small num-
ber of samples inclusions also were identied
by micro-Raman spectroscopy. Because pyropes
are largely free of diagnostic inclusions, the 2002
study identied mineral inclusions in just ve
samples (one Type I almandine and four Type II
almandines). Hence, although the large chemical
data set of Calligaro et al. (2002)—as expanded in
follow-up studies using the AGLAE proton probe
at the Louvre in Paris, France (see references cited
Table I: Various nomenclature schemes used for classifying historical garnets.
Calligaro et al.,
2002 Type I Type II Type III Type IV Type V
Gilg et al., 2010;
Gilg and Gast,
2012
Cluster B Cluster A Cluster C Cluster Z Group X Cluster D Cluster E
Chemical
characteristics
Mn-, Cr-
and Y-poor
almandine
Mn-, Cr-
and Y-rich
almandine
Ca- and
Mg-rich
almandine
Ca-rich,
Mg-poor
almandine
Intermediate
pyrope-
almandine
Cr-poor
pyrope
Cr-rich
pyrope
600 The Journal of Gemmology, 35(7), 2017
Feature Article
above)—continues to be the best resource on gar-
net chemistry available to date, only a statistically
insignicant amount of information on inclusions
was provided by these studies. Consequently, the
assignment of garnets to different types is at pre-
sent still based mainly on chemical data, and no
‘typical’ inclusion patterns derived from a similarly
large number of examined samples have been of-
fered to assist in classifying Type I to Type V gar-
nets. Furthermore, these studies did not indicate
the number of stones that could not be denitely
assigned to a specic type of garnet.
Such drawbacks were highlighted when Gilg et
al. (2010) observed that the two types of almandines
showed fairly consistent inclusion characteristics,
and the intermediate pyrope-almandines (Type
III) had extremely variable inclusion assemblages.
Thus, the latter could not be considered a ‘type’,
but rather were a group of different types. Gilg
et al. (2010) therefore used a somewhat different
nomenclature, subdividing the samples into Clus-
ters A through E and Group X (again, see Table I).
Four of the clusters paralleled four of Calligaro’s
types, and one, Cluster C, incorporated a new
chemically distinct group for Scandinavian stones
as characterized in previous studies (Löfgren, 1973;
Mannerstand and Lundqvist, 2003). The remaining
garnets formed the larger intermediate Group X,
which corresponded broadly to Calligaro’s pyrope-
almandine type but likely included multiple more
discrete types or clusters.
Thoresen and Schmetzer (2013) then com-
piled and compared properties of 37 garnets from
the ancient Greek and Roman eras with those
of early medieval samples. In that study, garnets
were found with compositions close to four of
Calligaro’s types: the two different types of early
medieval almandines (Type I/Cluster B and Type
II/Cluster A), Cr-poor pyrope (Type IV/Cluster
D) and the large group of intermediate pyrope-
almandine (Type III/Group X). Conversely, no
Cr-rich pyropes were discovered. In addition,
the investigations identied, among the Greek
and Roman samples, a third type of almandine
that to date has not been seen in early medieval
jewellery. These almandines were distinguished
by their high Ca and Mn but very low Mg con-
tents. A small group of Greek and Roman stones
yielding a similar composition already had been
denominated Cluster Z by Gilg and Gast (2012;
see Table I). Still, notwithstanding such work, the
statistical data set for Greek and Roman jewellery
has remained small, and information about inclu-
sions or trace-element contents was not available
for all of these samples.
Thus, in summary, no clear and fully support-
ed boundaries for the different types or clusters
of historical garnets have yet been published. In
most studies, only average chemical composi-
tions and standard deviations for the types and
groups, or hand-drawn compositional elds in
binary plots, were provided for characterization.
Ideally, data dealing with major-, minor- and
trace-element compositions; with solid and uid
inclusion assemblages; and with zoning of such
chemical components and inclusions—all taken
from a sufciently large number of samples—
should be utilized to dene a type or cluster.
Such complete data sets, however, do not yet ex-
ist or have not yet been published. Consequently,
for samples with overlapping chemical composi-
tions, the need persists to nd additional well-
dened criteria or establish denite inclusion pat-
terns, in order to support and better dene the
classication of historical garnets into types, clus-
ters or groups. In the process, for each group of
examined samples, the number of stones which
cannot be denitively assigned to a specic type
of garnet should be indicated.
Determining Geographic Origin of
Historical Garnets
Shortcomings also affect efforts to take the next
step beyond type classication and to correlate
garnet types with supposed geographic origins.
Many studies have pointed to large countries (In-
dia, Sri Lanka), Indian states (Rajasthan, Orissa)
or regions (Bohemia) as the possible or probable
source of a certain garnet type, cluster or group.
Such assignments often have been based only on
similarities in chemical composition and have not
considered or presented adequate comparative
inclusion data. Moreover, a detailed discussion of
other geologically related and thus chemically sim-
ilar occurrences has rarely been offered. For exam-
ple, gem-quality Cr-poor pyropes with chemical
compositions identical to those assigned to Type
IV/Cluster D garnets have been mentioned from at
least three places that were accessible in ancient
and medieval times (Monte Suimo, Portugal; pos-
sibly the Jos Plateau, Nigeria [Garamantic garnets];
and Elie Ness, Scotland), the rst two of which
Garnets from Arikamedu and Garibpet, India
Feature Article
601
apparently even relate to sources mentioned in
ancient texts (Gilg et al. 2010). A further occur-
rence of pyrope (Mount Carmel, Israel; Mittlefe-
hldt, 1986) has, to the knowledge of the present
authors, been considered as a possible source of
historical garnets only briey by Gilg et al. (2010).
Such challenges are magnied in the case of
India, where, aside from the basic problem that a
specic source might have been completely ex-
hausted and thus be presently unknown as a gem
locality, the pertinent time span can be extensive
and poorly documented. More than a millennium
stretched between the last written record in late
antiquity and the beginning of mineralogical re-
search in India in the rst part of the 19th century.
Yet available recent summaries of gem garnet lo-
calities in India that might have supplied raw ma-
terial for ornamental or jewellery purposes mostly
repeat older references and do not provide prima-
ry data (e.g. Brown and Dey, 1955; Wadia, 1966;
Jyotsna, 2000). Likewise, recent summaries of
possible trade routes in antiquity (see, e.g., Borell-
Seidel, 2017; Larios, 2017; Seland, 2017; Thore-
sen, 2017) present only generalized overviews,
without referring to specic localities in detail.
Consequently, the most promising strategy, and
the one employed here, is to take a more compre-
hensive approach: After considering the potential
sources mentioned in the literature, gem-quali-
ty material is obtained from likely localities for
examination and comparison with properties of
the historical garnets in question, incorporating
a large number of samples and multiple criteria.
The current study presents for the rst time
a thorough chemical and mineralogical charac-
terization of garnets found at the Arikamedu ar-
chaeological site in southern India (e.g. Figure
1), using high-quality major- and trace-element
data in conjunction with detailed inclusion stud-
ies. The authors then demonstrate a remarkable
correlation with recently mined garnets from Gar-
ibpet in Telangana State, India—approximately
640 km away or 760 km distant by road—as the
source of origin. Potential relationships of the Ari-
kamedu and Garibpet garnets to those excavated
at additional localities and to engraved samples, as
well as a discussion of possible trade routes, will
be the subjects of future publications.
Background
The Arikamedu Site and Its
Connection to Garnet Beads
Arikamedu is a highly signicant historical loca-
tion in India and has sparked great interest within
the archaeological community. The site is situated
on the banks of the Ariyankuppam River, approxi-
mately 4 km south of the town of Pondicherry
(Puducherry), in the state of Tamil Nadu in south-
east India (Figure 2). Arikamedu was discovered
in the 1930s and was excavated by British-Indian
(R. E. M. Wheeler, campaign of 1945), French (J.-M.
Casal, campaigns of 1947–1950) and American-
Indian archaeological teams (V. Begley, campaigns
of 1989–1992). These excavations unearthed nu-
merous archaeological artefacts of Roman origin
and led to Arikamedu being initially portrayed as
a Roman settlement (Wheeler et al., 1946; Casal
1949; Wheeler, 1954). Continued research, how-
ever, has shifted modern theories toward inter-
preting Arikamedu as an important Indian trading
centre and harbour, connecting the east coast of
India with the Western world from the 1st century
bc to the 7th century ad (Begley, 1983, 1993; Beg-
ley et al., 1996, 2004). Various trade routes from
the Indian east coast (Coromandel Coast) to the
west coast (Malabar Coast) have been established.
These included both land routes using the Palghat
Gap and sea routes via the Palk Strait between
India and Sri Lanka with smaller vessels or, later,
circumnavigating Sri Lanka with larger craft. The
Indian west coast was then linked with Mediter-
ranean society by means of major harbours, for
example Muziris (Ray, 1994; Smith, 2002; Deloche,
2010; Rajan, 2011; Gurukkal, 2013).
Figure 1: These faceted garnet beads were collected by local
farmers from the Arikamedu site. The samples constitute
some of those studied for this report (i.e. group B1) and
measure ~4.5–5.5 mm in diameter. Photo by K. Schmetzer.
602 The Journal of Gemmology, 35(7), 2017
Feature Article
Arikamedu has been equated with the harbour
of Podouke (Podukê) mentioned in the Peri-
plus Maris Erythraei (Periplus of the Erythraean
Sea), a sailing guide written by an anonymous
author in the 1st century ad (Raman, 1991). An-
other important ancient harbour also located on
the Coromandel Coast, south of Arikamedu, was
named Kaveripattinam (Rao, 1991a,b; Gaur and
Sundaresh, 2006; Sundaresh and Gaur, 2011). The
Kaveripattinam port has been associated with the
Kaberis Emporium cited by Ptolemy (Raman,
1991) and with a locality denominated ‘Caber’ in
a text by the traveller and merchant Cosmas In-
dicopleustes, written in the mid-6th century and
known as Christian Topography (Banaji, 2015; see
also Winstedt, 1909 and Schneider, 2011). It has
been speculated that the text mentioning “Caber
which exports alabandenum” refers to shipment
of almandine garnet (Roth, 1980; Kessler 2001).
After the decline in trade with the West, Ari-
kamedu trading activities focused on the East, as
demonstrated by the Chinese ceramics excavated
at the site (Begley et al., 1996, 2004). In the 19th
and 20th centuries, even after the archaeologi-
cal importance of the site had been recognized,
Arikamedu and surrounding regions continued
to be used for agriculture. Only in 2006 was the
land purchased by the government from private
landowners and designated a protected historical
site (Suresh, 2007).
In addition to its functions as port and trad-
ing centre, Arikamedu served as one of the main
bead-producing localities in India. The unearth-
ing of several thousand stone and glass beads
during the archaeological excavations attests
to this fact. Wheeler et al. (1946) mentioned
“more than two hundred beads of various ma-
terials found in the excavations” but did not re-
fer specically to garnets. Casal (1949) depicted
a limited number of garnets along with other
beads. Detailed information describing the ma-
terial excavated by Begley and her team in the
1989–1992 campaigns was published by Francis
(2002, 2004), who had joined in the archaeologi-
cal work. It was noted that garnets were the sec-
ond-most prevalent among the stone beads after
the quartz varieties. Francis (2004) listed about
3,500 pieces of glass beads and bead-making
waste that were excavated in the 1989–1992
campaigns together with 200 stone beads, in-
cluding 29 garnets. Numerous unworked garnet
pebbles were mentioned as well, exceeding the
number of nished beads.
The Pondicherry Museum houses 50,000
beads of multiple kinds, catalogued in a ‘bead
census’ by Francis (1986). This enormous num-
ber far surpasses the several hundred beads ex-
cavated by Wheeler and Casal. Francis (1987)
surmised that “the material was picked up on the
surface over the last 200 years or so” by villagers
living near Arikamedu. Garnet beads account for
10.1% of the Pondicherry Museum holdings of
stone beads (Francis, 2002). Francis (1991, 2001,
2004) assumed that beads were produced in Ari-
kamedu for over 2,000 years. Bead production re-
mained on-going in the region for centuries and
was only abandoned in the early 17th century. A
period when the site was uninhabited followed
thereafter for some time, with the area then see-
ing agricultural use in the 19th and 20th centuries
(S. Suresh, pers. comm., 2017). Francis (1993) in-
dicated that “the almandine garnets at Arikamedu
were doubtless from lower Andhra Pradesh”, but
he offered no denitive proof for this conclusion.
Garibpet
Arikamedu
Figure 2: This map of southern India shows the locations
of Arikamedu and Garibpet on the subcontinent. The
Arikamedu site is located adjacent to the Ariyankuppam
River, near the town of Pondicherry (neither of which are
shown at the scale of this map).
Garnets from Arikamedu and Garibpet, India
Feature Article
603
Although stone beads were mentioned in all
major excavation reports for Arikamedu (Wheel-
er et al., 1946; Casal, 1949; Wheeler, 1954; Begley
et al., 1996, 2004), only very limited information
about the garnet mineral species and composition
is available. The sole source of chemical data ex-
ists in the form of a summary published twice by
Francis (2002, p. 240; 2004, p. 480) of a micropro-
be analysis performed by C. Rösch at the Univer-
sity of Würzburg, Germany. The garnet, a surface
nd from Francis’s collection, was determined to
be composed of 83% almandine and 12% pyrope,
with spessartine and grossular being subordinate.
Unfortunately, the full analytical data underlying
the summary are no longer available (C. Wein-
furter, née Rösch, pers. comm., 2014). Thus, with
the possibilities offered by modern scientic in-
struments and methods, further investigation of
Arikamedu garnets may help answer heretofore
unresolved questions of historical signicance. In
particular, correlating Arikamedu samples with
medieval garnets could corroborate or disprove
origin theories and could conrm ancient trade
routes, as hinted at by the suggested association
of the ‘alabandenum’ from Caber with almandine.
Garibpet—History and Geology
Garibpet Hill is located south of the modern city
of Kothagudem in the Khammam District, Telan-
gana State, and southeast of the village of Garib-
pet (Figures 2 and 3; see also Master Plans India,
2014). Garibpet, Gharibpeth, Gharibpet, Gareeb-
Figure 3: The locations of Garibpet Hill and Garibpet village can be seen in this geological map, south of the municipality of
Kothagudem in the Khammam District, Telangana State, India. The Garibpet samples characterized in this study came from
the alluvial garnet deposit associated with Garibpet Hill. After Phani (2014b).
Sample site
Village, city
Lake
River
Road
Rail track
80°35'E 80°40'E
7°32'N
7°30'N
7°28'N
2 km
Strike and dip of
bedding/foliation
Fault or lithologic
contact
Alluvium (Quaternary)
Garnet-bearing
gravel and sand
Lower Gondwana Group
(Permian–Early Triassic)
Kamptee Formation
(conglomerate, sandstone)
Barakar Formation
(sandstone, shale, coal)
Talchir Formation
(sandstone, shale)
Khammam Schist Belt
(Vinjamuru domain)
(Early Proterozoic)
Garnet-kyanite-
muscovite schist
Garnet-biotite schist,
quartz-biotite schist
and gneiss
604 The Journal of Gemmology, 35(7), 2017
Feature Article
pet and several other variants of the name are
mentioned in the literature. Sometimes the local-
ity is also referred to as Palunsha or Paloncha,
now part of the modern city of Palvoncha, situ-
ated northeast of Kothagudem. Telangana State
was separated in 2014 from the neighbouring In-
dian state of Andhra Pradesh.
The Garibpet locality was rst described as a
secondary deposit and garnet mine by Voysey
(1833), the ‘Father of Indian Geology’ (Murty, 1982).
Many subsequent studies referred to this short note
by Voysey (e.g. Walker, 1841; Newbold, 1843), and
Walker also indicated that the material was cut in
Hyderabad. Bauer (1896) mentioned Garibpet as
a secondary occurrence of better-quality gem gar-
nets. Mirza (1937) then reported production gures
covering the period from 1910 to 1929. In addition
to discussing primary sources, Mirza observed that
“precious garnets are also reported in the water
courses draining the hills composed of garnetifer-
ous rocks” (see again Figure 3). The production
gures reect that the most extensive mining ac-
tivity during this period evidently occurred from
1915 to 1919, as follows (converted from pounds
to kilograms): 6,205 kg from 1910 to 1914, 105,513
kg from 1915 to 1919, 28,358 kg from 1920 to 1924,
and 12,902 kg from 1925 to 1929.
Researchers of the current era still recognize
the productive nature of the geology, with a recent
publication remarking that garnet-bearing schist
“constitutes an entire hill at Garibpet, in the Kham-
mam district” of Telangana State (Phani, 2014a).
Phani (2014a) further stated that in the Kothagu-
dem area “crystals of transparent to translucent al-
mandine variety of garnet occur in situ as well as
oat ore”. The garnets have been used both as an
abrasive and as a gem material (Kothagudem City,
2014). An analysis of Kothagudem garnet revealed
a composition of 85.0% almandine, 9.5% pyrope
and 0.9% spessartine (Kumar et al., 1992).
Garibpet is situated in the western part of
the Proterozoic Eastern Ghats Belt, close to the
north-west–south-east trending Permo-Triassic
Godavari Rift (Subbaraju, 1976; Phani, 2014b).
The Eastern Ghats Belt experienced two orogen-
ic episodes as a result of collisions between the
Archean Dharwar, Bhandara (Bastar) and Singh-
bum cratons in the west and cratonic areas of
Antarctica in the east. The late Paleoproterozoic
Krishna orogeny (~1.65 to 1.55 billion years [Ga])
occurred during the formation of the Columbia
supercontinent (Zhao et al., 2002), while the late
Mesoproterozoic to Neoproterozoic Grenvillian
orogeny started ~1.1 Ga during the assembly of
Rodinia (e.g. Dobmeier and Raith, 2003; Mukho-
padhyay and Basak, 2009; Dasgupta et al., 2013).
The Paleoproterozoic metamorphism prevails in
the western part of the Eastern Ghats Belt, the
so-called Krishna Province that is subdivided
into the western Nellore-Khammam schist belt
and the eastern granulite-facies Ongole domain
(Dobmeier and Raith, 2003). The Nellore-Kham-
mam schist belt comprises the upper, low-grade
Udayagiri domain and the lower, moderate-grade
Vinjamuru domain. The Kothagudem-Garibpet
area is located in the Vinjamuru domain of the
Khammam schist belt and consists of Paleoprote-
rozoic moderate-grade (and partly migmatitized)
metasediments and metavolcanics with minor
mac and granitic intrusives (Subbaraju, 1976).
Figure 4: (a) Shallow pits mark the locations of artisanal mining activities in this secondary deposit of garnet-bearing gravel in
the Garibpet area. Garibpet Hill is visible in the background. Photo by P. Périn, 2012. (b) The gravels consist mainly of garnet
pebbles (mostly ~0.5-1.5 cm in diameter). Photo by T. Calligaro, 2012.
ab
Garnets from Arikamedu and Garibpet, India
Feature Article
605
The conspicuous Garibpet Hill is formed of
garnet-kyanite-muscovite schist and is surrounded
by biotite schist and gneiss. The adjacent Goda-
vari Rift hosts clastic rocks composed of Lower
Gondwana sediments, including the Early Permian
terrestrial Talchir and Barakar Formations and the
Late Permian to Early Triassic Kamptee Formation.
The upper part of the Barakar Formation contains
signicant coal seams that make up the Kothagu-
dem Coal Field, with several underground work-
ings and the large Gautam Khani (or Goutham
Khani) open-cast mine located to the south of
Garibpet Hill (Figure 3).
The alluvial gem quality garnet-bearing gravels
occur on the west-north-western side of Garibpet
Hill and are derived from the weathering of the
garnet-bearing schist (again, see Figure 3). The
gravels are less than 1 m thick and consist mostly
of garnet pebbles (Figure 4). They continue to be
worked by local artisanal miners.
Materials and Methods
Sample Collection
In March 2014 one of the authors (JP) visited
Arikamedu, together with a local guide (Panjikar,
2014). During a walk across the site, beginning
at the ‘French mission house’, the guide found
various beads on the surface at several places.
The locations of these surface nds are shown in
Figure 5. Some beads were found in the roots of
fallen trees (e.g. Figure 6), while others were seen
in the sand along the banks of the Ariyankuppam
River. A preliminary examination at the Pangem
Sampling sites of garnet beads
Bricks
Excavation trenches
Figure 5: This schematic map of the
Arikamedu archaeological site indicates
where garnet beads in the form of
faceted bicones, typically broken, were
found. The arrow indicates the location
of the site shown in Figure 6. The inset
shows a sign marking the boundary of
the Arikamedu site. Photo by J. Panjikar;
map after Begley et al. (1996).
Figure 6: Various types of beads, including garnets, were found
on the surface at the Arikamedu archaeological site. Many
beads were discovered in the roots of trees and along the
banks of the Ariyankuppam River. Photo by J. Panjikar, 2014.
606 The Journal of Gemmology, 35(7), 2017
Feature Article
Group B4
Group A Group B1
Group C
Group B2 Group B3
Figure 7: These photos show the garnet samples from Arikamedu that were assembled for the present study and from which
selected samples were characterized. Group A: faceted bicones found at the archaeological site in 2014, with the largest
measuring ~4 mm in diameter. Groups B1 and B2: transparent faceted bicones collected by local farmers, with B1 samples
measuring ~4.5–5.5 mm in diameter and B2 samples being ~2.8–3.2 mm in diameter. Groups B3 and B4: translucent and
transparent spherical beads collected by local farmers, with B3 samples measuring ~5.2 mm in diameter and B4 samples
being ~3.2 mm in diameter. Group C: garnet fragments collected by P. Francis and archived at the American Museum of
Natural History, New York, USA, with the sample at top left measuring 9.0 × 6.8 mm. Photos by K. Schmetzer.
Testing Laboratory in Pune, India, revealed that
four different kinds of beads had been collect-
ed: blue glass, green glass, red to brownish red
glass and garnet. The garnet beads consisted of
broken and complete faceted samples, and 22 of
these were sent to Germany for further examina-
tion. All garnets of this group, designated group
A in the following text, were faceted in the form
of barrel-shaped bicone beads and were mainly
broken (Figure 7, upper left).
Garnets from Arikamedu and Garibpet, India
Feature Article
607
During her visit to Arikamedu, author JP was
informed by her guide that members of his fam-
ily possessed numerous similar beads that had
been unearthed in past decades during agricul-
tural work at or near the fenced archaeological
site, and a particularly substantial nd had been
made when local farmers were digging a well. A
portion of the garnets so discovered had been
kept within the guide’s family for at least two
generations. Ultimately, 314 such beads were ob-
tained from the family members and supplied for
examination. They are here designated group B
(Figure 7) and were visually sorted into four sub-
groups: faceted barrel-shaped bicones (groups
B1 and B2, identical in appearance to group A)
and smooth spherical beads (groups B3 and B4).
Group B1 consisted of 69 larger bicones ranging
from ~4.5 to 5.5 mm, and group B2 contained
55 smaller bicones of ~2.8–3.2 mm. Group B3
consisted of 60 larger translucent spherical beads
with a diameter of ~5.2 mm, and group B4 com-
prised 130 smaller transparent spherical beads of
~3.2 mm in diameter.
Although garnet samples from the Pondicher-
ry Museum were not available for non-destruc-
tive analyses and microscopic examination, the
authors were nonetheless able to obtain access
through an alternate channel to material that had
been collected by Peter Francis Jr. at Arikamedu.
After his death in 2002, bead research materi-
als remaining in Francis’s possession in the USA
were donated to the American Museum of Natu-
ral History in New York (see www.TheBeadSite.
com). Upon request, all samples in the red-to-
violet colour range within the container labelled
‘Arikamedu’, and thus potentially consisting of
garnets, were made available for study. In total,
31 samples were examined. Of those, 22 were
red-to-purple glass beads (e.g. Figure 8), one
was an amethyst and eight were garnets. The
eight garnets, designated group C for this project
(Figure 7), were all rough, primarily irregularly
shaped pieces without drill holes. As for the glass
beads, their visual appearance was such that,
without thorough gemmological examination,
some could be mistaken for garnets.
For comparative purposes, the study also in-
corporated rough material recently obtained from
the known garnet locality in Garibpet, India. Be-
cause initial research suggested that the proper-
ties of such samples correlated extremely well
with those of Arikamedu material, data on Gar-
ibpet stones was obtained to investigate the pos-
sibility of this deposit being a source of garnets
for the Arikamedu bead-making enterprise. The
garnet samples were collected in 2012 by two of
the authors (TC and PP) from a secondary depos-
it in the Kothagudem-Garibpet area (again, see
Figure 4) and are here designated group E. These
water-worn pebbles had somewhat rounded and
irregularly shaped surfaces, and were generally
covered by a weathered crust (Figures 9 and 10).
Although some of the samples were transparent
(group E1), most were only translucent at best
(group E2).
Sample Selection, Preparation and
Analytical Techniques
The garnets were initially examined with an im-
mersion microscope to provide information on
internal features and to guide selection of sam-
ples for more thorough investigation and analysis.
Figure 8: These red-to-purple glass beads from Arikamedu
were collected by P. Francis and archived at the American
Museum of Natural History, New York, USA. The sample at top
left measures 3.6 mm in diameter. Photo by K. Schmetzer.
Figure 9: These garnet pebbles (~0.5–1.5 cm in diameter and
coated by a weathered crust) were recovered from a secondary
deposit in the Garibpet area. Photo by T. Calligaro, 2012.
608 The Journal of Gemmology, 35(7), 2017
Feature Article
From the transparent Arikamedu beads (groups
A, B1, B2 and B4; see Figure 7), 41 were cho-
sen for electron microprobe analyses and detailed
inclusion examination, including identication by
micro-Raman spectroscopy. These examples cov-
ered all the different types of inclusion patterns
seen in the various beads. For the primarily bro-
ken bicones (group A), smaller faceted bicones
(group B2) and smaller transparent spherical
beads (group B4), a single at face was polished
on each sample for microprobe analysis. From
the larger faceted bicones (group B1), 11 beads
were cut in half using a diamond wire saw, and
the sawn surfaces of both halves were polished for
analysis (Figure 11). The same sawing procedure
was employed for ve translucent spherical beads
that contained opaque veinlets of foreign material
(group B3). Six irregularly shaped samples from
the Francis collection at the American Museum of
Natural History (group C) were analysed on a suit-
able rough surface without preparatory cutting or
polishing. A similar method had previously been
used successfully for the garnet beads excavat-
ed at Tissamaharama, Sri Lanka (Schüssler et al.,
2001). From the water-worn pebbles collected at
Garibpet, 15 samples were sliced in half, and both
resultant surfaces were polished. Seven of these
garnets (group E1) were comparable with the
transparent samples from Arikamedu (groups A,
B1, B2, B4 and C), and the other eight (group E2)
contained opaque polycrystalline seams or vein-
lets comparable with the translucent Arikamedu
samples (group B3). The analysed garnets of the
different groups are listed in Table II.
Electron microprobe analysis was carried out
using a JEOL JXA 8800L instrument equipped with
wavelength-dispersive spectrometers. Analytical
conditions were as follows: 15 kV accelerating volt-
age, 20 nA beam current, 1 µm beam diameter and
counting times of 20 s for peak positions and 20 s
for background. Natural and synthetic silicate and
oxide mineral standards or pure-element stand-
ards supplied by Cameca were used for calibra-
tion (i.e. andradite for Si and Ca, hematite for Fe,
Cr2O3 for Cr, corundum for Al, MnTiO3 for Mn and
Ti, and MgO for Mg). Kα radiation was utilized in
the process, and matrix correction was performed
by a ZAF procedure. Under these conditions, the
detection limit was ~0.05 wt.% for most elements,
and the analytical precision was better than 1%
relative for all major elements.
For all samples from Arikamedu with the ex-
ception of the garnets from group C, from four
to 12 single point analyses were performed on
their cut/polished surfaces. Appropriate locations
were selected on the rough fragments of group C
for a similar number of single point analyses per
stone. Additionally, for two faceted beads (group
B1) and two spherical beads (group B3), detailed
line-scans consisting of 29–49 point analyses per
scan were obtained. For the samples from Gar-
ibpet (without drill holes), complete line-scans
were performed across the cut and polished sur-
faces of all 15 garnets, consisting of 12–53 point
analyses within a single scan. In summary, a total
Figure 10: Among the garnet pebbles from the secondary
deposits in the Garibpet area, it is possible to nd
transparent samples of facetable quality. The pebbles range
up to ~1.5 cm in diameter. Photo by T. Calligaro, 2012.
10 mm
Figure 11: Faceted garnet bicones from Arikamedu were cut
in half and polished for microprobe analysis. Two drill holes
meet approximately in the centre of each sample. Photo by
H. A. Gilg.
Garnets from Arikamedu and Garibpet, India
Feature Article
609
Table II: Samples and techniques for microprobe analyses of garnets from Arikamedu and Garibpet, India.
Designation Description No. of drill-
holes
No. of
analysed
samples
Cut and/or
polished for
analysis
Analysis
techniquea
No. of point
analyses
Arikamedu
Group A
Faceted transparent
bicones, mostly broken 210 Yes 1 60
Arikamedu
Group B1
Larger faceted
transparent bicones 211 Ye s 1, 3 (for two
samples) 123b + 60c
Arikamedu
Group B2
Smaller faceted
transparent bicones 24Ye s 124
Arikamedu
Group B3
Larger translucent
spherical beads 1 5 Yes 1, 3 (for two
samples) 58b + 80c
Arikamedu
Group B4
Smaller transparent
spherical beads 116 Yes 1 96
Arikamedu
Group C
Irregularly shaped
fragments, transparent None 6 No 2 24
Garibpet
Group E1
Irregularly shaped water-
worn transparent pebbles None 7 Yes 3 (for all
samples) 192
Garibpet
Group E2
Irregularly shaped water-
worn translucent pebbles None 8 Ye s 3 (for all
samples) 137
a 1 = several point analyses on a cut and/or polished face; 2 = several point analyses on a at rough surface; 3 = continuous scans across a cut
and polished face.
b Number of individual point analyses.
c Number of point analyses within continuous scans across cut and polished faces.
of 854 point analyses were acquired from the Ari-
kamedu and Garibpet samples for this study (see
again Table II).
Trace elements in the garnets were analysed
by laser ablation inductively coupled plasma
mass spectrometry (LA-ICP-MS) using a short-
pulsed (<4 ns) UP193Fx argon-uoride fast-ex-
cimer laser ablation system (New Wave Research
Inc.) inductively coupled to an Agilent 7300c
plasma quadrupole mass spectrometer system
with an He-Ar carrier gas mixture. Single-spot
ablation (30–50 µm spot size) was conducted
with a laser frequency of 20 Hz, an irradiance of
0.69 GW/cm² and a uence of 3.41 J/cm². Data
reduction was carried out using Glitter 4.4.4 soft-
ware, with Si measured by the electron micro-
probe as an internal standard. The glass standard
NIST SRM 612 (Pearce et al., 1997) was used for
external calibration. Four large faceted bicones
and two larger spherical beads from Arikamedu
(groups B1 and B3) and seven garnets from Gar-
ibpet (groups E1 and E2) were selected for scans
consisting of three to eight spot analyses from
centre to rim.
A Leica DM LM polarising microscope with
transmitted and reected light sources and an
Olympus DX stereomicroscope, both equipped
with an Olympus DP25 digital camera and Olym-
pus Stream Motion software, were used for mi-
croscopic investigation and documentation of
inclusions. All mineral phases were addition-
ally identied by micro-Raman spectroscopy by
means of a Horiba Jobin Yvon XploRA PLUS
confocal Raman microscope. The spectrometer
was equipped with a frequency-doubled Nd:YAG
laser (532 nm, with a maximum power of 22.5
mW) and an Olympus 100× long working-dis-
tance objective with a numerical aperture of 0.9.
Results
Arikamedu Garnets—Visual Appearance
The garnets from Arikamedu comprised both
beads (groups A, B1, B2, B3 and B4) and irreg-
ularly shaped fragments (group C). The beads
were either faceted bicones or smooth spheres.
The bicones, all transparent, showed two parallel
planar facets, on opposite ends, into which the
holes through the beads had been drilled (Fig-
ures 12 and 13). The holes had been made from
each end, meeting approximately in the centres
of the bicones, and were cylindrical in shape
(Figures 11 and 14). The bead surfaces sloped
outward from each at end, creating a rounded
610 The Journal of Gemmology, 35(7), 2017
Feature Article
area, followed by two rows of facets around the
sides. The two angled rows of facets intersected
to form the widest diameter of the bicone beads.
2
4
1
3
Figure 12: This schematic drawing of a faceted bicone
from Arikamedu shows various features: (1) drill hole,
(2) planar unpolished facet used as a base for the drill hole,
(3) somewhat rounded area and (4) polished facet. Drawing
by K. Schmetzer.
Figure 13: Shown here are various
faceted bicones from Arikamedu. Each
sample has planar unpolished facets
serving as a base for the drill holes,
and a somewhat rounded area between
these planar surfaces and the rows
of polished facets. If the alignment of
facets in the two rows is mirrored across
the centre junction, a straight sequence
of edges is formed around the bicones
(bottom row, centre); if the alignment
or the number of facets in the two
rows differs, a zigzag pattern of edges
is found around the circumference
(bottom row, right). The beads measure
2.8–5.5 mm in diameter. Photos by
K. Schmetzer.
Measurements at these widest points versus
those between the drilled planar facets reected
ratios such as 5.0/4.2 mm, 4.1/3.6 mm or 3.4/3.1
mm.
The number of polished facets in each of the
two rows ranged from between 8 and 10 on the
larger beads to between 7 and 9 on the smaller
beads (Figure 13). Typically, the total count of
facets per row for any particular bead was iden-
tical (e.g. 9/9 or 8/8), but some beads exhibited
different numbers of facets within their two rows
(e.g. 7/8 or 7/9). The alignment of facets with-
in the two rows could be mirrored across the
centre junction, forming a more-or-less straight
sequence of edges around the cross-sections of
the beads. Conversely, where the facets in the
two rows varied in position or number, a zigzag
pattern of edges was seen around the centre cir-
cumference (again, see Figure 13).
The spherical beads comprised either smaller
transparent stones (Figure 14) or larger trans-
lucent samples (Figure 15). In detail, the larger
garnets contained some transparent areas inter-
spersed with opaque polycrystalline veins of
foreign materials (Figure 15). Both the smaller
and the larger spherical beads showed only a
single, conically shaped drill hole.
Garnets from Arikamedu and Garibpet, India
Feature Article
611
The contrast shown by the drill holes within
the faceted bicones versus the spherical beads in-
dicated different drilling techniques. According to
Gwinnett and Gorelick (1987) and Gorelick and
Gwinnett (1988), conically shaped drill holes are
commonly observed in Asian material and are
made by various simple tools. Cylindrically shaped
drill holes, on the other hand, are produced by di-
amond drills, most likely by the so-called twin dia-
mond drills. Analogous observations with respect
to drilling methods have also previously been
made in connection with an Arikamedu sample
(Gwinnett and Gorelick, 1988), thus supporting
the proposed manufacturing techniques.
The remaining samples from Arikamedu con-
sisted of rough, irregularly shaped pieces without
drill holes. The fragments were primarily trans-
parent. In visual appearance, they resembled the
excavated garnets depicted by Casal (1949).
All samples from Arikamedu, regardless of
group, were homogeneous purplish red to red-
dish purple, occasionally with a slightly brownish
modier, and without any colour zoning discern-
ible to the unaided eye.
Garibpet Garnets—Visual Appearance
The material from Garibpet (groups E1 and E2)
consisted of waterworn pebbles covered by a
weathered crust and, prior to preparation for
testing, had not undergone further processing or
fashioning. After being cleaned or polished on
the surface, the diaphaneity of the gem-quality
samples examined varied from translucent to ful-
ly transparent. Their colour appeared identical to
that of the garnets from Arikamedu, and no col-
our zoning was observed with the unaided eye.
Chemical Properties
Compositional Fields and End-Member Percent-
ages: The great majority of analysed samples
from Arikamedu, including both beads and frag-
ments (groups A, B and C), and the rough stones
from Garibpet (group E) proved to be garnets
with high almandine content. Microprobe data
revealed almandine in the range of 77–84 mol%,
with minor components of pyrope, spessartine
and grossular. Calculations based on some of the
854 point analyses indicated the presence of a
small andradite (Fe3+) component of up to 2.0%;
other garnet end members were negligible. Table
III summarizes the results of the chemical analy-
ses by electron microprobe.
A ternary plot of the molecular percentages
of the garnet end members pyrope and alman-
dine and the sum of spessartine + grossular
showed that the studied garnets plotted within
a relatively small compositional range (Figure
16a). This outcome was seen even more clearly
when only a small portion of the full ternary dia-
gram was drawn with an extended scale (Figure
16b). Various binary diagrams representing the
Figure 14: All faceted garnet beads from Arikamedu show
two cylindrical drill holes meeting approximately at the
centre (top row, ~5 mm in diameter). In contrast, spherical
garnet beads from Arikamedu show only a single slightly
tapered drill hole (bottom row, ~3.2 mm in diameter).
Photos by K. Schmetzer.
Figure 15: An irregular fracture is present in this translucent
spherical garnet bead from Arikamedu. The sample
measures ~5.2 mm in diameter. Photo by K. Schmetzer.
612 The Journal of Gemmology, 35(7), 2017
Feature Article
main cations replacing one another within the
solid-solution series pyrope-almandine-spessar-
tine-grossular (i.e. Mg-Fe-Mn-Ca; Figure 17) also
were helpful in elucidating the relatively small
compositional range and the overlap of chemi-
cal properties for samples from Arikamedu and
Garibpet.
The compositional elds for all but one of
the transparent Arikamedu samples obtained by
author JP at the archaeological site and from lo-
cal residents (groups A, B1, B2 and B4) showed
a complete overlap and, hence, are not reported
separately. The compositions of the larger trans-
lucent garnet beads from Arikamedu containing
veinlets of iron oxides and hydroxides as weath-
ering products (group B3) were found to be in
the same range, as were ve of the six analysed
garnets from the Francis collection (group C).
The samples from Garibpet, both transparent
(group E1) and translucent (group E2), likewise
evidenced substantial overlap in composition-
Table III: Microprobe analyses of garnets from Arikamedu and Garibpet, India.a
Locality Arikamedu Garibpet
Group A, B1, B2, B4 B3 C E1 E2
Description
Transparent
faceted bicones
or spherical
beads
Translucent
spherical beads
Transparent
irregularly shaped
fragments
Transparent
pebbles
Translucent
pebbles
Composition (wt.%)
SiO235.42–37.03 35.96–37.28 34.58–37.79 34.74–36.84 35.18–36.72
TiO2nd–0.05 nd–0.05 nd–0.05 nd–0.06 nd–0.07
Al2O321.02–22.28 21.66–22.22 21.46–22.75 20.55–22.24 21.10–21.97
Cr2O3nd–0.08 nd–0.08 nd–0.05 nd–0.08 nd–0.09
Fe2O3
b0.29–3.25 0.59–2.73 0.29–4.64 0.42–3.48 0.45–2.91
MnO 0.41–2.32 0.75–1.43 0.59–1.37 0.50–2.38 0.51–2.58
MgO 2.52–3.37 2.83–3.57 2.96–3.27 2.42–2.99 2.37–2.99
CaO 0.34–0.90 0.60–0.93 0.47–0.82 0.47–0.73 0.48–0.73
FeOb34.50–37.20 35.05–36.90 34.08–37.33 34.05–37.20 0.45–2.91
FeOtotal 36.38–38.76 36.41–38.33 36.92–39.03 36.39–38.88 36.30–39.21
Mol% end membersc
Almandine 77.6–83.5 77.7–82.3 77.4–81.9 79.4–83.4 79.2–84.0
Pyrope 10.2–14.2 11.3–14.1 11.8–13.0 9.8–12.0 9.6–12.0
Spessartine 0.9–5.3 1.7–3.2 1.3–3.1 1.1–5.5 1.2–5.9
Grossular 0.9–2.5 1.6–2.5 1.3–2.5 0.6–2.1 1.1–2.1
a The composition of two anomalous samples from Arikamedu (see Figure 16a) are not included here, since they apparently represent garnets
from different primary sources. Abbreviation: nd = not detected.
b FeO and Fe2O3 were calculated from FeOtotal by stoichiometry.
c Small andradite contents (up to 2.0 mol%) are not included.
al elds. No differences in chemical composi-
tion were found between ‘clean’ samples and
those with veins lled by secondary weathering
and oxidation processes, regardless of whether
the material was from Arikamedu or Garibpet.
Thus, the compositional elds for the two ma-
jor groups considered here (i.e. samples from
Arikamedu and Garibpet) were in close proxim-
ity and overlapped to a large extent, as demon-
strated in Figures 16 and 17. Neglecting the small
andradite percentages, the compositional ranges
for the two localities were:
•Arikamedu: 77.4–83.5% almandine, 10.2–14.2%
pyrope, 0.9–5.3% spessartine, 0.9–2.5% grossular
•Garibpet: 79.2–84.0% almandine, 9.6–12.0% py-
rope, 1.1–5.9% spessartine, 0.6–2.1% grossular
Notably, these almandine contents are in the
upper range or even slightly above the values
typically observed for gem-quality almandine
from other modern localities (Stockton and Man-
son, 1985).
Garnets from Arikamedu and Garibpet, India
Feature Article
613
lower in garnets from Arikamedu (Figure 17b,d).
Nonetheless, it should be emphasized that, al-
though the average compositions were slightly
different, samples from Arikamedu and Garibpet
cannot be separated using a single point analy-
sis, due to the wide overlap in the compositional
ranges for both groups.
Garnet Composition
Mol% end members
10
20
30
40
50
60
70
80
90
Pyrope
Almandine Spessartine + Grossular
90
80
70
60
50
40
30
20
10
10 20 30 40 50 60 70 80 90
Pyrope
Almandine Spessartine + Grossular
Spessartine
+ Grossular
Almandine
Pyrope
1.3 2.5 3.8 5.0 6.3 7.5 8.8 10.1 11.3
19.2
18.0
16.7
15.4
14.2
12.9
11.7
10.4
9.1
+ Transparent bicones and spherical beads
+ Translucent spherical beads
+ Fragments collected by P. Francis
+ Transparent pebbles
+ Translucent pebbles
Arikamedu
Garibpet
Figure 16: (a) This ternary diagram shows
the chemical composition of garnets
from Arikamedu and Garibpet calculated
for the molecular end-members pyrope,
almandine and spessartine + grossular.
The compositions plot in a concen-
trated area, except for two anomalous
Arikamedu samples (blue and purple
arrows) that fall outside the main com-
positional eld, which are inferred to be
from different sources. (b) An enlarged
detail of the main compositional eld for
the Arikamedu and Garibpet garnets cor-
responds to the area dened by the grey
triangle in the inset. Note the extensive
overlap in the composition of garnets
from Arikamedu and Garibpet.
Oxide weight percentages further revealed
that the average MgO content in Arikamedu sam-
ples was slightly higher than in Garibpet garnets
(Figure 17a–c). The average CaO value was also
slightly higher for garnets from Arikamedu (Figure
17a). In contrast, the average MnO content was
slightly greater in Garibpet samples and slightly
a
b
614 The Journal of Gemmology, 35(7), 2017
Feature Article
There were also two exceptions to the above
typical composition, and they were found amongst
the samples from Arikamedu (see Figure 16a).
One of the beads from group A consisted of 68.4%
almandine, 27.1% pyrope, 0.5% spessartine and
1.1% grossular, and one garnet from the Francis
collection showed 38.9% almandine, 45.8% py-
rope, 2.5% spessartine and 10.4% grossular. Given
the notable divergence from the compositional
ranges for the vast majority of the Arikamedu and
Garibpet stones, these two garnets most likely rep-
resent samples from other primary sources, and
they presumably came to Arikamedu from locali-
ties other than Garibpet.
For general interest, some of the 22 purplish
red glass beads from Arikamedu that had been
collected by Francis were analysed as well. These
samples contained unusually high manganese
contents in the range of 4.5 wt.% MnO and rela-
tively low iron percentages of 0.9 wt.% FeO.
Chemical Zoning of Major and Minor Elements:
Additional chemical detail was obtained from
analytical traverses across the undrilled water-
worn pebbles from Garibpet. All of these line-
scans showed a decrease in Mn from core to rim
of the garnet crystals, which correlated with an
increase in Mg (Figure 18). Prominent Mn zona-
tion is characteristic of prograde garnet growth
(e.g. Spear, 1995), and such zoning has been
reported from several locations (e.g. Lanzirotti,
1995; Borghi et al., 2000). Calcium zoning was
less pronounced but still frequently observed.
Calcium levels decreased slightly from the core
2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
MgO (wt.%)
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
CaO (wt.%)
Chemical Composition
3.0
2.7
2.4
2.1
1.8
1.5
1.2
0.9
0.6
0.3
0
MnO (wt.%)
+ Transparent bicones and spherical beads
+ Translucent spherical beads
+ Fragments collected by P. Francis
+ Transparent pebbles
+ Translucent pebbles
Arikamedu
Garibpet
2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
MgO (wt.%)
40.0
39.6
39.2
38.8
38.4
38.0
37. 6
37. 2
36.8
36.4
36.0
FeOtotal (wt.%)
0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0
MnO (wt.%)
40.0
39.6
39.2
38.8
38.4
38.0
37. 6
37. 2
36.8
36.4
36.0
FeOtotal (wt.%)
2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
MgO (wt.%)
Figure 17: Various binary plots show the chemical composition of Arikamedu and Garibpet garnets, calculated as MgO, CaO, MnO
and FeO weight percentages. Again, the plots show extensive overlap in the compositions for garnets from Arikamedu and Garibpet.
a
cd
b
Garnets from Arikamedu and Garibpet, India
Feature Article
615
outwards and, after a minimum, then reversed di-
rection to increase slightly toward the outermost
rim (again, see Figure 18). In some scans, only a
portion of the patterns depicted in Figure 18 was
apparent, as expected when examining samples
derived from secondary deposits in the form of
water-worn pebbles, since some of the crystals
were broken or abraded and did not represent
the complete as-grown garnets.
The four line-scans performed across samples
from Arikamedu (two faceted bicones and two
spherical beads) revealed the same basic chemi-
cal zoning as the Garibpet samples. Again, how-
ever, because these beads consisted of only a part
of the original as-grown crystals, the scans corre-
sponded merely to a portion of the full area from
core to rim and back. More specically, the scans
across the two spherical beads represented an
area that could be described as the core plus in-
ner rim, while the scan across one faceted bicone
represented an area from core to rim and the scan
across the other bicone represented an area from
the rim to the core and then to the inner rim.
Crystal Chemistry: Upon plotting the atomic pro-
portions of the main bivalent cations Mg (rep-
resenting pyrope), Fe (representing almandine),
Mn (representing spessartine) and Ca (represent-
ing grossular), an inverse correlation between Mg
and Mn (Figure 19a) and between Mg and Fe
(Figure 19b) was observed. Again, comparing the
samples from Garibpet and Arikamedu, slightly
3.0
2.5
2.0
1.5
1.0
0.5
0
Concentration (wt.%)
1 3 5 7 9 1 1 1 3 1 4
Analysis Point
Rim Core Rim
Garibpet Garnet Compositional Zoning
Electron Microprobe Analyses
MnO
CaO
MgO
1 9 17 25 33 41 49 53
Analysis Point
3.2
2.8
2.4
2.0
1.6
1.2
0.8
0.4
Rim Core Rim
Concentration (wt.%)
1 5 9 13 17 21 23
Analysis Point
3.0
2.6
2.2
1.8
1.4
1.0
0.6
0.2
Rim Core Rim
Concentration (wt.%)
1 5 9 13 17 21 25
Analysis Point
Rim Core Rim
Concentration (wt.%)
3.0
2.5
2.0
1.5
1.0
0.5
Figure 18: Line-scans by electron microprobe across four garnet samples from Garibpet show chemical zoning of MnO, CaO
and MgO. From the core to the rim, MnO decreases and MgO increases; CaO exhibits a subtle but more complex pattern.
616 The Journal of Gemmology, 35(7), 2017
Feature Article
Garnet Composition
Atomic Proportions
+ Transparent bicones and spherical beads
+ Translucent spherical beads
+ Fragments collected by P. Francis
+ Transparent pebbles
+ Translucent pebbles
Arikamedu
Garibpet
95.4
90.8
86.1
81.5
76.9
72.2
67.6
63.0
58.4
4.6 9.2 13.9 18.5 23.1 27.8 32.4 37.0 41.6
Mg
Ca Mn
Mg
Mn
Ca
1.4 2.7 4.1 5.5 6.8 8.2 9.6 10.9 12.3
Fe Ca
Mg
Mg
Ca
Fe
19.0
17.6
16.2
14.9
13.5
12.1
10.8
9.4
8.0
Figure 19: These ternary diagrams
show the chemical composition of
garnets from Arikamedu and Garibpet,
calculated according to atomic
proportions for: (a) Mg, Ca and Mn; and
(b) Mg, Fe and Ca. Both plots display
enlarged details of the full triangular
diagrams, as shown by the grey
triangles in the insets. The data show
an inverse correlation between Mg and
Mn (a) and between Mg and Fe (b).
elevated Mg (pyrope) contents were found in
Arikamedu garnets, with higher Fe (almandine)
and Mn (spessartine) proportions seen in garnets
from Garibpet. As previously noted, the composi-
tional ranges for the Arikamedu samples obtained
on author JP’s visit and those from the Francis
collection were substantially equivalent, and the
overlap with the Garibpet garnet chemistry was
extensive. The results exhibited for both the Ari-
kamedu and the Garibpet garnets were consist-
ent with an isomorphic replacement of Mg by
Mn, which was dominant, and a replacement of
Mg by Fe, which was subordinate. This isomor-
phic substitution can be represented by the gen-
a
b
Garnets from Arikamedu and Garibpet, India
Feature Article
617
Table IV: LA-ICP-MS analyses of garnets from Arikamedu and Garibpet, India.
Locality Arikamedu Garibpet
No. samples 6 7
No. analyses 30 31
Element (ppmw) Mean Minimum Maximum Mean Minimum Maximum
Li 22 16 27 22 15 28
P232 154 371 227 122 313
Ca 3454 2652 4414 3308 274 6 5055
Sc 95 74 125 79 55 112
Ti 39 17 61 38 18 55
V 29 19 43 28 17 44
Cr 64 28 198 55 25 255
Mn 8747 3422 17456 11494 3451 19494
Co 33 23 56 33 19 41
Ni 0.5 0.3 1.0 0.6 0.3 1.1
Zn 129 88 159 107 77 129
Y261 88 548 213 45 401
Zr 6 1 17 4111
eral scheme Mg (Mn, Fe), applicable to all of
the Arikamedu and Garibpet samples. For crystal
chemistry considerations, Ca was correlated with
Mn in the core of the samples and with Mg in
the rim (Figure 18). This leads to a replacement
scheme of Mg (Mn, Fe, Ca) for the core and
(Mg, Ca) (Mn, Fe) for the rim of the garnets.
Thus, in general, the small changes in Ca values
representing slightly different grossular compo-
nents were negligible.
Trace Elements: Trace-element contents yielded
by LA-ICP-MS are summarized in Table IV. Both
the compositional averages and the ranges dem-
onstrated by the analyses were nearly identical
for the Arikamedu and Garibpet garnets. A similar
relationship was noted for lanthanide rare-earth
elements (not shown in Table IV). Several sam-
ples from Arikamedu and Garibpet also showed
chemical zoning for some trace elements, such
as Y, P and Zn. Levels of certain other trace ele-
ments were nearly constant within the scans.
Considering in detail both trace and other ele-
ments as measured by LA-ICP-MS, chemical zon-
ing between core and rim was strong for Mn and
signicant for Ca, largely consistent with the re-
sults of microprobe analyses. The continuously
decreasing Mn contents within scans from core to
rim correlated with an increase in Ca and Zn and
a systematic decrease in P. Yttrium levels varied
but typically in a random way, displaying only mi-
nor, and often no, systematic variation between
core and rim (Figure 20). The relatively high Y
concentrations in the Arikamedu and Garibpet
garnets are indicative of a temperature range
of ~550–600°C during formation, if buffered by
xenotime (Pyle and Spear, 2000). Titanium levels
were low (17–61 ppm) and showed a moderate
decrease from core to rim.
Inclusions
Insofar as all investigated garnets from Arikamedu
had inclusion characteristics identical to those
seen in the Garibpet samples, the results are pre-
sented together here. The garnets exhibited a very
typical zonation with an inclusion-rich core and
a rather inclusion-poor rim (Figures 21a,b and
22). The cores reached a diameter of ~2–3 mm,
while the rims had a maximum width of ~3–4
mm. Consequently, the small beads and frag-
ments sometimes displayed inclusion features
corresponding only to the core or the rim, but
not both. The proto- to syngenetic inclusions in
the cores comprised, with decreasing abundance:
apatite, quartz, ilmenite, rutile, monazite, zircon,
graphite and uid inclusions. The elongated in-
clusions at times showed a preferential orienta-
tion, marking in part a wavy schistosity inherited
618 The Journal of Gemmology, 35(7), 2017
Feature Article
from the metamorphic host rock. At the core-rim
boundary, a very characteristic layer of brous
sillimanite bundles was observed. The sillimanite
bres in some instances reached far into the in-
clusion-poor rims. Isolated zircon, monazite and
quartz crystals also were found occasionally in
the rims. The garnets were often cut by brown-
ish-yellowish fractures coated by various genera-
tions of goethite or other iron oxides-hydroxides.
Apatite (Figure 21c,d) occurred as elongated,
sometimes segmented, euhedral prismatic crys-
tals up to 600 µm long and 60 µm in diameter,
with subrounded tips. The apatite was colour-
less and contained characteristic aky rounded
opaque inclusions up to 20 µm in diameter that
Raman microspectroscopy identied as graphite.
Apatite was not observed in the inclusion-poor
rims of the garnets.
Quartz (Figure 21e,f) was found as rounded
to subrounded isometric and elongate transparent
grains, as well as occasional polycrystalline aggre-
gates with straight grain boundaries. The aggre-
gates were more common in the inclusion-poor
rims and were up to 1 mm long. Also observed
was an unusual ring-shaped quartz inclusion.
Sillimanite (Figure 21g,h) was mainly seen at
the core-rim boundaries. The brous curved ag-
gregates of colourless needles exhibited a diameter
of less than 10–30 µm (Figure 23) but reached a
length of more than 1 mm. Some acicular silliman-
ite crystals also continued to grow into the inclu-
sion-poor rims of the garnets (Figure 24).
Monazite (Figure 25a,b) was observed as short
prismatic crystals, easily recognizable by their
brownish halos, rounded shapes and inclusion-
rich nature. The inclusions consisted of opaque
phases, identied by Raman analyses as graph-
ite, as well as high-relief colourless rutile crystals.
Anhedral monazites up to 60 µm were seen. The
monazite inclusions only exceptionally induced
fractures in the host garnets.
Zircon (Figure 25c,d) was found as euhe-
dral prismatic crystals and was primarily colour-
less. In contrast to the monazite inclusions, zir-
con almost always produced tension fractures.
Ilmenite (Figure 25e,f) often formed rounded,
or more rarely subhedral, opaque akes of up
to 300 µm in diameter. These akes occurred
within the cores of the garnet crystals in groups
frequently recognizable with the unaided eye. In
rare cases, highly irregular shapes were found.
With reected light (Figure 25g,h), the internal
structure of the opaque akes was visible on cut
surfaces and showed many rounded inclusions
up to 20 µm in diameter. Raman spectroscopy
identied these inclusions as quartz.
Rutile (Figure 26a,b) occurred mostly in the
form of a three-dimensional network of extreme-
Garibpet Garnet Compositional Zoning
LA-ICP-MS Analyses
MnO (wt.%)
CaO (wt.%)
Core
Y (ppmw)
P (ppmw)
Zn (ppmw)
CoreRim Rim
3.0
2.5
2.0
1.5
1.0
0.60
0.55
0.50
0.45
0.40
120
110
100
90
80
250
200
150
100
300
200
100
0
1 mm
Figure 20: LA-ICP-MS analyses show
chemical zoning between the core
and rim in a garnet from Garibpet.
Variations are seen in two primary
garnet compositional elements, Mn and
Ca (left), and in the trace elements Y, P
and Zn (right). The analysis points are
shown by the circles on the photo of the
sample. Photomicrograph by H. A. Gilg.
Garnets from Arikamedu and Garibpet, India
Feature Article
619
ly thin needles oriented along [110] or [111] direc-
tions of the host, found exclusively in the cores of
the zoned garnets. The distribution of the orient-
ed needles was, however, quite patchy, and many
inclusion-rich cores lacked such a rutile network.
More rarely a second type of rutile was found
as brownish translucent euhedral overgrowth
rims on opaque ilmenite cores (Figure 26c,d).
Fluid inclusions (Figure 26e,f) were present
in planar arrays along healed fractures, thus in-
dicating their secondary nature. They always
displayed a very rugged, irregular surface. Their
visual aspect suggested either textural re-equili-
bration or retrograde reactions with the host, syn-
chronous to the formation of colourless Fe-rich
chlorite crystals. Some fractures appeared to have
monophase inclusions without vapour bubbles,
while others exhibited a vapour bubble lling ap-
proximately 40% of the inclusion’s volume.
Secondary fractures (Figure 26g,h) were lled
with polycrystalline material. Raman microspec-
troscopy identied them as primarily iron oxides
and hydroxides (see also Figure 15).
The complete inclusion pattern just demon-
strated has not yet been described for any his-
torical garnet. However, it should be emphasized
Arikamedu Garibpet
a
2 mm
50 μm
500 μm
b
100 μm
c
200 μm
d
500 μm
ef
500 μm
g
500 μm
h
Figure 21: A comparison of the
inclusion pattern found in garnets from
Arikamedu (left) and Garibpet (right)
revealed very similar features which
include: (a,b) zoning of inclusions in
the core ‘C’ and rim ‘R’ of the samples,
with ‘s’ representing a zone enriched
in tiny sillimanite bres; (c,d) apatite;
(e,f) quartz; and (g,h) sillimanite bres.
Photomicrographs by H. A. Gilg.
620 The Journal of Gemmology, 35(7), 2017
Feature Article
that the most characteristic feature—the zone of
ne sillimanite bres—while rare among garnets
in general, is not unique. A similar rim of silli-
manite bres surrounding a core with numerous
inclusions such as biotite, ilmenite and rutile was
described recently from north-eastern Connecti-
cut, USA (Axler and Ague, 2015).
Discussion and Conclusions
Garnets found at Arikamedu, historically one of
the most important bead-producing locations in
India, were characterized and compared to sam-
ples collected from an alluvial deposit in the Gar-
ibpet area, located approximately 640 km north
of Arikamedu. In particular, six criteria were con-
sidered to evaluate whether the Arikamedu gar-
nets were originally sourced from Garibpet:
1. Chemical composition, namely in terms of
the percentage of garnet end members
2. Chemical zoning for major and minor ele-
ments within the crystals from core to rim
3. Trace-element contents
4. Zoning of trace elements from core to rim
5. General inclusion assemblage
6. Distribution and zoning of inclusions
The authors suggest that such criteria are key
in any endeavour to establish a common source
for groups of gem samples, including historical
material. In applying these criteria to garnets
from Arikamedu and Garibpet, the following re-
sults were obtained:
a. Broad overlap in the population elds for
the chemical composition of samples from
both localities, with a nearly identical aver-
age and only small differences
b. An identical scheme of chemical zoning
from core to rim for major and minor ele-
ments
c. The same group of trace elements in essen-
tially identical percentage ranges
d. A consistent situation with respect to zon-
ing of trace elements with insignicant vari-
ability for most elements and distinct zoning
for some others (e.g. Y, P and Zn in several
samples)
e. The same general assemblage of inclusions,
incorporating numerous specic minerals
(mainly apatite, quartz, ilmenite, rutile, mon-
azite, zircon and sillimanite)
200 μm
5 mm
Figure 22: Zoning of inclusions in a garnet pebble from Gar-
ibpet shows a heavily included core and a more transparent
rim. In the transition area is a zone enriched with a high con-
centration of tiny sillimanite bres (visible at higher magni-
cation; see, e.g., Figure 23). Photomicrograph by H. A. Gilg.
Figure 23: Tiny sillimanite bres are shown here at high
magnication in a transparent garnet bead from Arikamedu.
Black-and-white photomicrograph by H. A. Gilg.
0.1 mm
Figure 24: Coarse acicular sillimanite needles were
observed in a small number of the garnets from Arikamedu.
Photomicrograph by H. A. Gilg.
Garnets from Arikamedu and Garibpet, India
Feature Article
621
f. A consistent zoning of inclusions between
core and rim, with the boundary separating
these two zones being enriched with brous
sillimanite needles
Given the detailed consistency of features
listed above for the chemical criteria 2, 3 and 4,
and very similar properties related to end-mem-
ber composition populations (criterion 1), the
authors are convinced that the garnets worked
at the bead-making site of Arikamedu originated
from the Garibpet area. The small differences ob-
served in the average chemical compositions can
probably be explained by the fact that the Garib-
pet samples were collected from one secondary
source within a large garnet-bearing area (which
includes the primary source of Garibpet Hill)
and, therefore, are not entirely representative of
the Garibpet rough material used for bead pro-
duction at Arikamedu. However, neither detailed
data for garnets collected at various places within
the extensive Garibpet area, nor a comparison
of samples found within the secondary garnet-
bearing gravels and the primary garnet-bearing
host rock, is presently available.
Arikamedu GaribpetGaribpet
g
100 μm
a
50 μm
b
50 μm
c
50 μm
d
e
500 μm
f
500 μm
100 μm
h
200 μm
Figure 25: Very similar inclusion patterns
are seen in garnets from Arikamedu
(left) and Garibpet (right), including: (a,b)
monazite with graphite and rutile inclu-
sions; (c,d) zircon with tension cracks; (e,f)
ilmenite akes; and (g,h) ilmenite akes
with quartz inclusions. Photomicrographs
by H. A. Gilg in transmitted light (a–f) and
reected light (g,h).
622 The Journal of Gemmology, 35(7), 2017
Feature Article
The Arikamedu-Garibpet garnets characterized
in this study plot—according to chemical compo-
sition and depending on the type of plot and the
elements selected—within or close to one of the
major types or clusters of garnets established for
early medieval samples, namely within Type I of
Calligaro et al. (2006–2007) or Cluster B of Gilg
et al. (2010). However, they are distinguishable
by their higher Mn, Cr and Y concentrations. This
scenario suggests a potential problem of excessive
breadth in the existing denitions circumscribing
the types or clusters. Such breadth, in turn, calls
into question the usefulness of these categories,
not only for understanding relationships amongst
historical and/or contemporary samples but also
for guiding origin determination. The overlap is
mostly due to the poor quality of some (but not
all) chemical analyses (H. A. Gilg, unpublished re-
search). Indeed, by considering only good-quality
analyses (i.e. those with a garnet composition and
formula close to ideal or at least acceptable garnet
stoichiometry), there is a reduction in overlap and
a better denition of garnet types or clusters.
With respect to the general inclusion assem-
blage and inclusion zoning (criteria 5 and 6), the
data for the Arikamedu and Garibpet samples are
Arikamedu GaribpetArikamedu Garibpet
a
200 μm
b
200 μm
c
200 μm
d
200 μm
e
50 μm
f
50 μm
g
2 mm
h
5 mm
Figure 26: Additional characteristic
inclusion patterns in garnets from
Arikamedu (left) and Garibpet (right)
include: (a,b) networks of rutile nee-
dles; (c,d) transparent rutile overgrowth
on opaque ilmenite crystals; (e,f) uid
inclusions; and (g,h) secondary frac-
tures lled with polycrystalline material,
primarily iron oxides and hydroxides.
Photomicrographs by H. A. Gilg.
Garnets from Arikamedu and Garibpet, India
Feature Article
623
quite consistent, thereby supporting the relation-
ship indicated by their composition. Conversely,
no inclusion pattern similar to that described for
the Arikamedu/Garibpet samples has been seen
by the authors to date in garnets from numerous
recent productive localities in India and Sri Lanka.
Again, however, it must be emphasized that a
particular group of inclusions alone should not be
relied upon as sufcient for origin determination.
For instance, samples excavated in Unterhaching,
Bavaria, which plot chemically in the Type II/
Cluster A compositional eld, display an inclu-
sion pattern consisting of rutile needles, zircon,
quartz, sillimanite and ilmenite (Gast et al., 2013).
This clearly demonstrates the possibility of simi-
lar and partly overlapping inclusion assemblages
among garnets from different origins and dictates
that all features of such inclusion patterns should
be considered. To give an illustrative example,
the characteristic graphite-bearing apatite inclu-
sions found in Garibpet and Arikamedu garnets
are absent from Type II/Cluster A garnets.
Hence, the authors suggest that the results of
the present study should prompt a re-evaluation,
at least partly, of the established types or clusters.
On a general level, it has become apparent that
some of the types or clusters might consist of sev-
eral subgroups and should be split accordingly.
More specically, in doing so, the methodology
should perhaps be rened beyond a simple nar-
rowing of compositional ranges. Because it re-
mains possible, and even likely, that there will be
samples from different origins with overlapping or
similar chemical compositions, regardless of the
ranges chosen, the following two queries should
be considered. First, how many criteria should be
used to dene the types or clusters? Second, how
many such criteria would any given sample need
to full before being assigned to a particular type
or cluster? In some cases, it may be feasible only
to offer probabilities of assignments.
The authors are of the opinion that the tradi-
tional practice of using mainly chemical compo-
sition, occasionally supplemented by identica-
tion of a few inclusions (not a complete pattern
incorporating any possible zoning), is decient.
As one example of the shortcomings of the cur-
rent method, two garnets set in a Hellenistic gold
earring described by Gartzke (2004) plot within
the same compositional eld as the Arikamedu-
Garibpet samples (for further details, see Thore-
sen and Schmetzer, 2013). Without considering
multiple additional features, however, it is clear
that such information offers only minimal sup-
port for drawing any conclusions regarding the
provenance of these two Hellenistic garnets.
Thus, we feel that a more detailed correlation
of properties is necessary to assign a sample to
an established type or cluster of garnets. Stated
otherwise, only samples which full more than
one, or preferably more than two, criteria (tak-
ing into account the concentrations of all meas-
ured main, minor and trace elements as well as
the type, shape and distribution of inclusions)
should be assigned to a particular garnet type or
cluster. Conversely, any proposed assignment of
samples that correspond only in one feature (e.g.
in chemical composition) should be indicated as
not assigned with certainty.
Some of the early medieval garnets classied
as Type I/Cluster B, with the underlying analyses
derived mostly from excavated jewellery pieces,
overlap in chemical composition with the range
determined for the Arikamedu-Garibpet samples.
Other criteria pertaining to the early medieval sam-
ples, however, are unavailable or vague. Hence,
at a minimum, further detailed inclusion studies
would be necessary to establish whether the same
inclusion assemblage, and especially the zoning
of inclusions with a sillimanite-enriched boundary,
is present in the medieval garnets. Such examina-
tions could go far in proving or disproving wheth-
er stones from the Garibpet deposit were used
for early medieval cloisonné metalwork jewellery.
In forthcoming studies, the results described
in this article will be compared with those de-
rived for garnets from other excavations—such as
stones from Tissamaharama, Sri Lanka—and with
properties of engraved early medieval samples.
As a harbinger of such future work, the authors
would highlight that a Byzantine garnet, engraved
with a Christian motif and dated to the end of the
6th or beginning of the 7th century ad, has shown
consistency with the Garibpet material in average
chemical composition, chemical zoning, inclusion
assemblage and inclusion zoning. This, in turn,
could have signicant implications for establishing
whether the text of Cosmas Indicopleustes (see
Banaji, 2015), written in the mid-6th century ad,
refers to the shipment of Garibpet garnets from
harbours located on the Coromandel Coast at or
close to Arikamedu.
624 The Journal of Gemmology, 35(7), 2017
Feature Article
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The Authors
Dr Karl Schmetzer
85238 Petershausen, Germany
Email: SchmetzerKarl@hotmail.com
Prof. Dr H. Albert Gilg
Lehrstuhl für Ingenieurgeologie, Technische
Universität München, 80333 Munich, Germany
Prof. Dr Ulrich Schüssler
Institut für Geographie und Geologie,
Universität Würzburg, 97074 Würzburg, Germany
Dr Jayshree Panjikar FGA
Panjikar Gem Research & Tech Institute,
Pune 411001, India
Dr Thomas Calligaro
Centre de Recherche et de Restauration des
Musées de France, 75001 Paris, France
Patrick Périn
Directeur honoraire du Musée d’Archéologie
Nationale, 08220 Rubigny, France
Acknowledgements
The authors are grateful to Lorann S.A.
Pendleton and Dr David H. Thomas (Division
of Anthropology, American Museum of Natural
History, New York, New York, USA) for the
loan of garnet and glass samples collected at
Arikamedu by Peter Francis, Jr. Prof. Dr Peter
Gille (Department of Earth and Environmental
Sciences, Ludwig-Maximilians-University,
Munich, Germany) assisted in sawing the
beads examined for this study, and Vladimir
Ruttner (Engineering Geology, Technical
University of Munich) prepared the polished
sections. Dr Helene Brätz (Geo-Center of
Northern Bavaria, Erlangen, Germany), is
thanked for measurement and evaluation of
the LA-ICP-MS analyses. Prof. S. Suresh
(Chennai, India) provided helpful information
about the history of Arikamedu.
... The characteristics of inclusions can be identified by Raman microspectroscopy. In garnets, solid inclusions are mostly found in almandines, pyrope-almandines and pyropes, although various inclusions or textures may be observed in other types of garnets as presented in Table 1, depending on the environment of formation and origin [30,31]. Table 1. ...
... Table 1. Commonly recognized solid inclusions in garnets [30,31]. By determining the chemical composition and, in rare cases, even the mineral inclusions of Merovingian Kingdom (mid-5th-7th century AD); gemstones from France, Belgium and South Germany; and five different types of garnets and their probable geographical-geological origin have been possible to be identified to date (e.g., [2][3][4][5][6][7][8][9]). Two types of almandine, group of garnets with the intermediate composition of pyrope-almandine (also in terms of gemmology-rhodolite or pyraldine, e.g., [5]) and two types of pyrope were determined. ...
... Optical microscopy and Raman spectroscopy used in inclusion analysis show that mostly apatite, monazite, zircon, uraninite, xenomorphic Fe-chlorite, and rarely rutile, were present in Type I almandines. On the other hand, for type II almandines, xenomorphic quartz crystals, ilmenite, zircon, uraninite, monazite, rutile needles and sillimanite were identified [4,8,31,32]. The latter might indicate the formation in high metamorphic rocks [31,32]. ...
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Garnets (19 pieces) of Late Antique Sfibulae from the archaeological site at LajhKranj (Slovenia) were analysed with Raman microspectroscopy to obtain their mineral characteristic, including inclusion assemblage. Most garnets were determined as almandines Type I of pyralspite solid solution series; however, three garnets showed a higher Mg, Mn and Ca contents and were determined as almandines Type II. Most significant Raman bands were determined in the range of 169–173 cm−1 (T(X2+)), 346–352 cm−1 (R(SiO4)), 557–559 cm−1 (ν2), 633–637 cm−1 (ν4), 917–919 cm−1 (ν1), and 1042–1045 cm−1 (ν3). Shifting of certain Raman bands toward higher frequencies was the result of an increase of the Mg content in the garnet composition, which also indicates the presence of pyrope end member in solid garnet solutions. Inclusions of apatite, quartz, mica, magnetite, ilmenite, as well as inclusions with pleochroic or radiation halo and tension fissures (zircon), were found in most of the garnets. Rutile and sillimanite were found only in garnets with the highest pyrope content. Spherical inclusions were also observed in two garnets, which may indicate the presence of melt or gas residues. The determined inclusion assemblage indicates the formation of garnets during medium- to high-grade metamorphism of amphibolite or granulite facies. According to earlier investigations of the garnets from Late Antique jewellery, the investigated garnets are believed to originate from India.
... In recent years, the study of garnet beads and jewellery using compositional analysis has expanded in many areas of Europe and South Asia (e.g. Quast and Schüssler 2000;Gilg et al. 2010;Carter 2016;Schmetzer et al. 2017). In contrast, the region of Northeast Africa has remained largely ignored despite its strategic ...
... The reference garnets from Wadi Abu Dom and Wadi el-Haraz (AD, EH) were analyzed with a JEOL JXA 8800L electron microprobe equipped with a wave-dispersive X-ray spectrometer at the Chair of Geodynamics and Geomaterial Research of the Julius-Maximilians-University of Würzburg (e.g., Schmetzer et al. 2017;Gilg et al. 2018). We used an accelerating voltage of 15kV, a beam current of 20nA, beam diameter of 1μm, counting times of 20 s for peak positions and 20s for the background. ...
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Outstanding garnet beads were found recently in an elite tumulus dated to the fourth century AD and located at the cemetery of Hagar el‐Beida in the Upper Nubian Nile Valley region. Whereas contacts of Northeast Africa with South Asia have just been proven through analysis of glass beads found in Nubia and dating to the time of intensive Indian Ocean trade, scientific evidence for Nubia's link with the regions to the west was lacking. Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) was used to determine the elemental composition of three garnet beads to gain information about their type and origin. Additionally, we analyzed twelve garnets from two nearby alluvial placer deposits. While the garnet beads are inclusion‐free Cr‐poor and Ti‐rich pyropes related to alkaline mafic volcanic rocks, the local garnet deposits are shown to be inclusion‐rich almandines and thus unrelated to the investigated Nubian beads. Detailed comparison of data from Merovingian cloisonné jewellery and all known sources of the Cr‐poor and Ti‐rich pyropes shows identical ranges of elemental contents. The source of raw materials for the beads found in Nubia has been not identified with certainty yet, but sources in Portugal and Nigeria are suggested and a connection is shown to similar garnets from Merovingian contexts.
... Garnets. In attempting to identify the origin of the garnets, the authors referred to the classification of Gilg et al. (2010) and Schmetzer et al. (2017). These authors classified ancient Greek, Roman, and Early Medieval garnet-bearing jewels according to five main type clusters, based on their chemical composition, and related to this the calculated percentages of the different pure end members of the pyralspite and ugrandite garnets as well as their chromium and yttrium content. ...
... These authors classified ancient Greek, Roman, and Early Medieval garnet-bearing jewels according to five main type clusters, based on their chemical composition, and related to this the calculated percentages of the different pure end members of the pyralspite and ugrandite garnets as well as their chromium and yttrium content. Raman peak positions and chemical signatures (a major almandine component with relatively high Y concentration) indicate that almost all of the garnets set in the talisman correspond to cluster A (historical garnets originating from southern India or Sri Lanka in the Middle Ages) as described by Gilg et al. (2010) and Schmetzer et al. (2017). We therefore assume they originated from southern India or Ceylon. ...
... ). Durch weitere Arbeiten konnten diese Typen den Abbauregionen Indien, Sri Lanka, Böhmen, Portugal und Schweden zugeordnet werden(z. B. Greiff 1998;Périn et al. 2007; Gilg et al. 2010;Schmetzer et al. 2017; Greiff 2018). Die Ergebnisse sind am besten in einem Ca/Mg-Diagramm darzustellen(Abb. ...
... századforduló vízválasztó időszak a provenienciakutatások számának ugrásszerű növekedése miatt. A műszeres analitikai módszerek fejlődésével és gyarapodásával egyre több külföldi és hazai régészeti gyűjtemény ékköves anyagáról készült archeometriai elemzés (a legfontosabbak : Greiff 1998;Calligaro et al. 2002;Mannerstrand & Lundqvist 2003;Gilg et al. 2010;Horváth & Bendő 2011;Schmetzer et al. 2017;Calligaro & Périn 2019;Pion et al. 2020;Then-Obłuska et al. 2021). A nemzetközi kutatás eredményei alapján az elmúlt évtizedekben folyamatosan fejlődik a régészeti korokban felhasznált gránátok geokémiai (ásványkémiai) meghatározása és osztályozása. ...
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A nagyváradi csüngő különleges tárgy, annak ellenére, hogy típusára, kialakítására nézve nem rendkívüli darab a polikróm ötvösmunkák körében. Ráadásul régészeti kontextusa is ismeretlen, mivel szórványként került elő. Ezt a gránátberakásos aranyékszert sajátos története emeli ki a többi közül, ami több szálon és több idősíkban fut. Előkerülése a régmúlt időkbe nyúlik vissza, amikor az efféle tárgyakra inkább személyes kincsként, mintsem régészeti leletként tekintettek. Ez adhat magyarázatot arra, hogy a tárgy, megtalálását követően, újra használatba került. A csüngő történetéből egy család története bontakozik ki, közel hozva a 19. századi szellemiséget. Az egykori kézműves munkájához pedig egy modern ötvös kapcsolódott, aki a régit újjal kiegészítve egyedülálló alkotást hozott létre. A nagyváradi csüngő személyes tárgy volt, és a régészeti leletek többségével szemben, előkerülése után is az maradt még egy jó ideig. Bár végül múzeumba került, viszonylag kevéssé ismert; nincs kiállítva és alig szerepel a szakirodalomban. Ami pedig korábban megjelent róla, az is átértékelésre szorul. Jelen írásunk ezen az állapoton kíván változtatni, bemutatva és értelmezve a tárgyon elvégzett szisztematikus archeometriai vizsgálat eredményeit. A komplex elemzések segítségével sikerült meghatározni a tárgy anyagi és technológiai jellemzőit: az ékkőberakások gemmológiai és ásványtani sajátosságait, a fémes alapanyag kémiai (elemi) összetételét, a készítés egyes munkafázisait. Az eredmények kiértékelésével olyan alapvető kérdésekben juthattunk előrébb, mint a gránátok eredete, kereskedelme, az arany alapanyag lehetséges előélete, a készítés infrastrukturális háttere, továbbá a tárgy keltezése és kulturális kontextusa. A csüngő azon ritka esetek közé tartozik, amikor az ékkőberakások megmunkálásának módja, technikája korjelző szerepet játszik. Ennek a felismerésnek különösen egy szórvány lelet esetében van régészeti jelentősége. A tárgy ez alapján a hun korban, az 5. század első felében készülhetett, fémes alapanyaga nem származhatott közvetlenül másodlagosan felhasznált római solidus-ból, de részben tartalmazhatott ilyen minőségű aranyat. Jelenlegi ismereteink szerint, eredeti gránátberakásai Srí Lankából, ékkőpótlása pedig a 19. századi Csehországból eredeztethető.
... Provenance studies of the tiny garnet inlays have come into focus since the end of the last century. Thousands of analyses and many field trips in present-day, or at one-time, mine districts facilitated their increasingly detailed geochemical characterisation (recently: Schmetzer et al., 2017;Calligaro and Périn, 2019;Then-Obłuska et al., 2021). The identification and comparison of (mineral and fluid) inclusions and chemical compositions (major, minor and trace elements) with similar datasets of recent geological samples has proved to be the key to the localisation of potential geological sources. ...
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The use of non-destructive and non-invasive analytical methods is widespread in the archaeometric study of metal objects, particularly in the case of precious metal artefacts, from which sampling is not, or in a limited way, allowed due to their high value. In this study, we highlight the main advantages and limitations of non-destructive analytical methods used on three polychrome animal-style silver buckles from the mid-to-late-5th-century Carpathian Basin. Optical microscopic observations, handheld XRF, SEM-EDX and μ-XRD analyses were performed to determine the chemical composition of the metals and their decoration (gilding, garnet and niello inlays), as well as the microtexture and mineralogical composition of the niello, in order to gain a better understanding of the materials used and reconstruct the manufacturing techniques in detail. The buckles were manufactured from relatively high-quality silver derived from the re-use of gilded silver scrap metal and intentionally alloyed with brass or leaded brass. The presence of mercury indicated the use of fire gilding. The niello inlays are composed of mixed silver-copper sulphides, even reaching the composition of pure copper sulphide; this is for the first time, when copper sulphide niello is observed on a silver object. The almandine garnets most probably originate from Southern India and Sri Lanka.